Triphenylphosphine-mediated serendipitous synthesis of alkyl cinnamates through the reaction of 3-hydroxy-4-methoxybenzaldehyde and dialkyl acetylenedicarboxylates

Article abstract of DOI:10.1080/104265090917664

Alkyl cinnamates are formed in fairly good yields from the reaction of dialkyl acetylenedicarboxylates and 3-hydroxy-4-methoxybenzaldehyde in the presence of triphenylphosphine. Copyright Taylor & Francis Inc.

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Triphenylphosphine-Mediated
Serendipitous Synthesis of
Alkyl Cinnamates Through
the Reaction of 3-Hydroxy-4-
Methoxybenzaldehyde
and Dialkyl
Acetylenedicarboxylates
Issa Yavari a , Hoorieh Djahaniani a , Logman Moradi
a & Farough Nasiri a
a Department of Chemistry, Tarbiat Modarres
University, Tehran, Iran
Version of record first published: 19 Aug 2006
To cite this article: Issa Yavari, Hoorieh Djahaniani, Logman Moradi & Farough
Nasiri (2005): Triphenylphosphine-Mediated Serendipitous Synthesis of Alkyl
Cinnamates Through the Reaction of 3-Hydroxy-4-Methoxybenzaldehyde and Dialkyl
Acetylenedicarboxylates, Phosphorus, Sulfur, and Silicon and the Related Elements,
180:9, 2149-2153
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Phosphorus, Sulfur, and Silicon, 180:2149–2153, 2005
Copyright © Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/104265090917664
Triphenylphosphine-Mediated Serendipitous
Synthesis of Alkyl Cinnamates Through the Reaction
of 3-Hydroxy-4-Methoxybenzaldehyde and Dialkyl
Acetylenedicarboxylates
Issa Yavari
Hoorieh Djahaniani
Logman Moradi
Farough Nasiri
Department of Chemistry, Tarbiat Modarres University, Tehran, Iran
Alkyl cinnamates are formed in fairly good yields from the reaction of dialkyl
acetylenedicarboxylates and 3-hydroxy-4-methoxybenzaldehyde in the presence of
triphenylphosphine.
Keywords 3-Hydroxy-4-methoxybenzaldehyde; alkyl cinnamates; dialkyl acetylenedi-
carboxylates; triphenylphosphine
α, β-Unsaturated esters are useful chemical entities which are
accessible through condensation reactions involving aldehydes, viz.
(i) Knoevenagel condensations of active methylene esters with
aldehydes,1 (ii) condensation of alkyl acetates with aldehyde followed
by dehydration,2 and (iii) Hornet, Wadsworth-Emmons olefination of
carbonyl compounds.3 The Knoevenagel condensation route, partic-
ularly for cinnamic esters, involves two separate steps, i.e., (1) the
preparation of cinnamic acid (2) followed by its esterification and Refor-
matsky reaction, which has the limitation of not being suitable for the
preparation of cinnamic acids with halo, phenoxy, or nitro substituents
on the aromatic moiety.4
We have recently described5 the synthesis of functionalized couma-
rine derivatives from the reaction of triphenylphosphine, dimethyl
acetylenedicarboxylate (DMAD), and phenols using an intramolecu-
lar Wittig reaction. With the purpose of preparing coumarine deriva-
tives that have a methoxy group at position 8 and a carbaldehyde
Received November 4, 2004; accepted February 12, 2005.
Address correspondence to Issa Yavari, Department of Chemistry, University of
Tarbiat Modarres, PO Box 14115-175, Tehran, Iran. E-mail: isayavar@yahoo.com
2149

2150
I. Yavari et al.
SCHEME 1
group at position 5, 1 (Scheme 1), 3-hydroxy-4-methoxybenzaldehyde
was treated with DMAD and triphenylphosphine. However, the
coumarine derivative 1 was not observed and methyl 3-hydroxy-4-
methoxycinnamate 4a was isolated instead in 60% yield (Scheme 2).
The reaction of 3-hydroxy-4-methoxybenzaldehyde with dialkyl
acetylenedicarboxylates in the presence of triphenylphosphine in
CH2Cl2 at room temperature proceeded smoothly and produced alkyl
(E)-(3-hydroxy-4-methoxyphenyl)-2-propenoates (alkyl cinnamates, 4)
in moderate yields (see Scheme 2). These products were separated by
column chromatography. The structures of compounds 4a–4d were de-
duced from their 1H NMR and 13C NMR spectroscopic data.
The 1H NMR spectrum of 4a exhibited two single sharp lines readily
recognized as arising from methoxy (δ = 3.78 and 3.90 ppm) group and
an AX pattern for the vinylic protons (δ = 6.30 ppm, 3 J = 16 Hz; and
HH
δ = 7.57 ppm, 3 J = 16 Hz), together with an AXM pattern for the
HH
3
3
aromatic protons (δ = 6.82 ppm, J = 8.2 Hz; δ = 7.01 ppm, J
=
HH
HH
4
4
8 Hz, and J = 2 Hz; and δ = 7.12 ppm, J = 2 Hz). The proton-
HH
HH
SCHEME 2

Synthesis of Alkyl Cinnamates
2151
SCHEME 3
decoupled 13C NMR spectrum of 4a showed 11 distinct resonances in
1
agreement with the proposed structure. The H and 13C NMR spectra
of 4b–4d are similar to those for 4a except for the ester moieties, which
give rise to characteristic signals in the aliphatic region of the spectra.
Partial assignment of these resonances is given in the Experimental
section.
The plausible way of formation of the product is proposed in
Scheme 3. On the basis of the well-established chemistry of trivalent
phosphorus nucleophiles,5−13 it is reasonable to assume that compound
4 results from the nucleophilic addition of triphenylphosphine to the
acetylenic ester and subsequent protonation of the reactive 1:1 adduct
by 3-hydroxy-4-methoxybenzaldehyde. Then the positively charged ion
undergoes a [2 + 2] cycloaddiotion reaction with the aldehyde carbonyl
group to produce the oxetane 7. The alkyl cinnamates 4 are presumably
produced by fragmentation of 7.
In conclusion, the reaction of dialkyl acetylenedicarboxylates and
3-hydroxy-4-methoxybenzaldehyde in the presence of triphenylphos-
phine provides a simple one-pot entry into the synthesis of alkyl (E)-
3-(3-hydroxy-4-methoxyphenyl)-2-propenoates. This procedure has the
advantages of mild reaction conditions and simple experimental and
work-up conditions.
EXPERIMENTAL
Melting points were measured on an Electrothermal 9100 appara-
tus. Elemental analyses for C, H, and N were performed using a
Heraeus CHN-O-Rapid analyzer. These results agreed favorably with
the calculated values. IR spectra were measured on a Shimadzu IR-
460 spectrometer. 1H and 13C NMR spectra were measured with
a Bruker DRX-500 AVANCE instrument with CDCl3 as solvent at
500.1 and 125.7 MHz, respectively. Mass spectra were recorded on
a Finnigan-Matt 8430 mass spectrometer operating at an ioniza-
tion potential of 70 eV. 3-Hydroxy-4-methoxybenzaldehyde, dialkyl

2152
I. Yavari et al.
acetylenedicarboxylates, and triphenylphosphine were obtained from
Fluka (Buchs, Switzerland) and were used without further purification.
Preparation of Methyl (E)-3-(3-hydroxy-4-methoxyphenyl)-
2-propenoate (4a)
To a stirred solution of 3-hydroxy-4-methoxybenzaldehyde (0.30 g,
2 mmol) and DMAD (0.28 g, 2 mmol) in CH2Cl2 (10 mL) was added
drop wise at −10◦C over 10 min a solution of triphenylphosphine (0.52 g,
2 mmol) in CH2Cl2 (5 mL). The reaction mixture was then allowed to
warm up to room temperature and stand for 24 h. The solvent was re-
moved under reduced pressure and product 4a was separated by silica
gel column chromatography (Merck 230–400 mesh) using n-hexane-
EtOAc as eluent. White powder; yield: 0.12 g (60%), mp 119–120◦C.
1
IR (KBr) (νmax/cm−1): 3395 (OH), 1693 (C O). H NMR (500.1 MHz,
CDCl3): δ = 3.78 (3 H, s, OMe), 3.90 (3 H, s, OMe), 5.80 (1 H, br s, OH),
3
3
6.30 (1 H, d, J = 16 Hz, CH), 6.82 (1 H, d, J = 8 Hz, CH), 7.01
HH
HH
(1 H, dd, 3 J = 8 and 4 J = 2 Hz, CH), 7.12 (1 H, d, 4 J = 2 Hz,
HH
HH
HH
CH), 7.59 (1 H, d, 3 J = 16 Hz, CH). 13C NMR (125 MHz, CDCl3): δ =
HH
51.6 (OMe), 56.00 (OMe), 110.5, 113.0, 115.8, 121.8 (4 CH), 128.0 (C),
144.7 (CH), 145.9 (C O), 148.6 (C O), 167.7 (C O).
Ethyl (E)-3-(3-hydroxy-4-methoxyphenyl)-2-propenoate (4b)
Yellow oil, yield: 0.14 g, (65%). IR (KBr) (νmax/cm−1): 3385 (OH), 1690
1
3
(C O). H NMR (500.1 MHz, CDCl3): δ = 1.20 (3 H, t, J = 7.1 Hz,
HH
Me), 3.79 (3 H, s, OMe), 4.13 (2 H, q, 3 J = 7 Hz, O CH2), 5.58 (1 H, br
HH
s, OH), 6.15 (1 H, d, 3 J = 16 Hz, CH), 6.71 (1 H, d, 3 J = 8 Hz, CH),
6.90 (1 H, dd, 3 J = H8Hand 4 J = 2 Hz, CH), 7.01 (1 H, d, 4 J = 2
HH
HH
HH
HH
Hz, CH), 7.45 (1 H, d, 3 J = 16 Hz, CH). 13C NMR (125 MHz, CDCl3):
HH
δ = 14.2 (Me), 56.0 (OMe), 60.4 (CH2), 110.5, 113.0, 116.4, 121.8 (4 CH),
128.2 (C), 144.4 (CH), 145.9 (C O), 148.5 (C O), 167.3 (C O).
iso-Propyl (E)-3-(3-hydroxy-4-methoxyphenyl)-2-propenoate
(4c)
Yellow oil, yield: 0.17 g, (75%). IR (KBr) (νmax/cm−1): 3390 (OH), 1687
1
(C O). H NMR (500.1 MHz, CDCl3): δ = 1.31 (6 H, d, 3 J = 7 Hz,
HH
3
2 Me), 3.76 (3 H, s, OMe), 5.09 (1 H, heptet, J = 7 Hz , OCH), 5.50
HH
(1 H, br s, OH), 6.27 (1 H, d, 3 J = 16 Hz, CH), 6.89 (1 H, d, 3 J = 8
HH
HH
Hz, CH), 6.91 (1 H, dd, 3 J = 8 and 4 J = 2 Hz, CH), 6.97 (1 H, d,
HH
HH
4 J = 2 Hz, CH), 7.59 (1 H, d, 3 J = 16 Hz, CH). 13C NMR (125 MHz,
HH
HH

Synthesis of Alkyl Cinnamates
2153
CDCl3): δ = 21.6 (Me), 55.9 (OMe), 67.3 (CH), 110.4, 113.3, 115.4, 121.4
(4 CH), 127.8 (C), 144.2 (CH), 145.7 (C O), 148.1 (C O), 167.8 (C O).
tert-Butyl (E)-3-(3-hydroxy-4-methoxyphenyl)-2-propenoate
(4d)
Yellow oil, yield: 0.16 g, (65%). IR (KBr) (νmax/cm−1): 3390 (OH), 1695
(C O). 1H NMR (500.1 MHz, CDCl3): δ = 1.49 (9 H, s, CMe3), 3.78 (3 H,
s, OMe), 5.67 (1 H, br s, OH), 6.34 (1 H, d, 3 J = 16 Hz, CH), 6.86 (1 H,
HH
d, 3 J = 8 Hz, CH), 7.0 (1 H, dd, 3 J = 8 and 4 J = 2 Hz, CH), 6.90
HH
HH
HH
(1 H, d, 4 J = 2 Hz, CH), 7.62 (1 H, d,3 J = 16 Hz, CH). 13C NMR
HH
HH
(125 MHz, CDCl3): δ = 28.3 (CMe3), 55.8 (OMe), 81.5 (O CMe3), 110.5,
113.3, 115.3, 121.6 (4 CH), 127.9 (C), 144.9 (CH), 145.8 (C O), 148.1
(C O), 168.0 (C O).
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